Worst thing possible an engine flush additive.
Worse still is neglected regular oil changes, creating the sludge.
Anyone worked out if this sludge is long life oil going bad or car service settings not changed from long life, but short life oil used?
Personally, I like engine flush great for unblocking gummed up hydraulic lifters, I use it every other oil change.
Very aware of the issues the OP experienced, but I have been lucky with every new to me car tI have used it on... mind you I am poring it in with one hand and fingers crossed with the other!